Synchronization of disk scanning means



July 8, 1941.

SCHLE SINGER SYNCHRONIZATION OF DISK SCANNING MEANS Filed Nov. 23, 1937 Q hie/7b My Patented July 8, 1941 SYNCHRONIZATION F DISK SCANNING Kurt Schlesinger, Berlin, Germany, asaignor, by mesne assignments, to Loewe Radio, Inc., a corporation of New York Application November 23, 1937, Serial No. 176,020

In Germany November 26, 1938 2 Claims.

The invention relates to television transmitters according to the interlaced line method. If the number of lines per image or frame amounts. to 400 or more a scanning disk is desired that, for

desired impulses.

(Chris-69.5)

It is seen, that the displacing fault can be reduced by a large proportion o. v

The invention will be iully understood fro the detailed description which will now be'given practical reasons, executes more than one revo- 5 of an exemplary embodiment thereof which islution per held, 1. e. in the case of two fields per illustrated in the accompanying drawing and frame or image, at least N= i revolutions per which shows a diagram of the optical and elec-. image. In the following N=4 and a line fretrical elements.

- quency f is supposed. p In the drawing 8 is the scanning disk provided It is known that in the interlacedline method 10 with a four-turn spiral of scanning apertures there is required for the beginning of each frame (not shown) and, for producing the synchronizachange impulse a precision which can be ensured tion signals, with a rim of slots 6 for the line and only by special'methods. The relation between a slot 9 for the frame impulses. 1 The number of the number of frame changes and the number of the slots 8 is equal to the numberof the desired line impulses must remain irrevocably constant, single impulses. Each of these two sy m 1 and the twov signals must begin completely indeslots is illuminated by a separate device. I'he pendently of each other. The method frequently lamp i (respectively H) projects light byway oi.

. employed of deriving the frame change impulses a condensing lens 2 (l2) onto a diaphragm 8 (l3) from the disk motor circuit-does not ensure adewhich is reproduced sharply onto the disk I by a quate precision and accordingly sufliciently r p u ln n 4 (ll). This re reduction is steady location of the two part images screens perf at h & Beale that e image of one within the other. The most steady image the ph a P lleed 0 the ll-8e U B Sma e was obtained by a purely optical method of signal than t redial height o e 8 0th- ThllB' It is generation. The line and frame synchronization avoi ed that-a fluttering of the disc influences signals are produced each by a separate photothe amp t of the sis l ans nt y th cell in conjunction with light-chopping slots in length 0 the l light 9 18 made qual o the the disk. The special method according to the distance between two B10t8.- In Eli-m8 way an invention consists in that the approximately pproxim l sinusoidal lilme curve all the p ir sinusoidal line synchronization signals are elec.-J ellellrrehtle e trically filtered by a tuned amplifier, reduced in so The light beam chopped by h isk e la confrequency a conv rt mm sharp impulses of ducted to the photo-cell at (so and converted line frequency whilst the frame impulses are into electrical currents. According to the inven aperiodically amplified, tion there are employed two entirely different According to the inv nti n, th number oi th electrical methods of treatment for the line and slots for producing the line synchronizing imlihellllime change pu sespulses is equal to the numberof the desired line The frequency S pp y the P -c l Z synchronizing impulses. Therefore, if multiple 8 equal to 4!. It is amp fi y h p y 8 revolutions per image are necessary, a multiple tive resonance circuit 05 e filte System num'ber of the synchronizing impulses are pro- A frequency reduce? 14 8 y lih on ed y lineduced by the disk. B using a disk producing a 40 e u y d upp ies in s qutw a sine oscilmultiple number of the desired impulses, the dis- 19171011 01 line frequency- A tim imphhle -v tortlons eiiected by the variations of the disverter c r the e osci s of he tances or apertures of the slots on the disk p'roline frequently into impulses oi' adiustable duraducing said impulses are reduced. The distor-' tion- 4 tions eiiect a displacing of the image. The dis h impulses pp y h P -cell 3i placing fault is are aperiodically amplified by means of a ree 1 sistance-coupled amplifier 33. Since the disk F p j 5;, rotates four times per image. it supplies four th m i impulses per image, whereas only two are req=a constant factor of the damping qll j=the frequency ofthe impulses produced The halving is'usually effected by a shutter. by the rotating disk. According to the invention, the problem is solved =the proportion of the number of the proin a more simple way y feedin the P l duced impulses to the number of the 3|, instead with D. 0., with alternating current 25 of frame frequency by means of a transformer ll, resistance 4 and condenser 42 serving for filtering out higher harmonics. It is presumed that the source 26 is the alternating voltage mains feeding the synchronous motor driving disk 8 and that the frame signal occurs at the maximum of that voltage. This way only every second light impulse is able to produce an electric impulse. Of course. the alternating voltage may, instead of to the photo-cell, also be applied is any stage of the following aperiodic amplifier 10 The output of the amplifier II and the output of the sine impulse converter 34 are connected to a mixing stage 35. In this stage the line synchronizing impulses and the frame impulses are mixedtogether.

Preferably the mixingstage ii is a tube having at least two independent series disposed control grids. In this case the outputs of "and N are connected each to one of the control grids. The tube is connected so that its anode current is interrupted at least by one of the impulses arriving at one of the grids.

For removing distortions of the amplitude of the signals effected by the relative movements between disk and light image it is proposed that on the disk is projected a sharply defined light image. The dimensions of this light image shall be smaller than those of the slots for producing the signals. 30

I claim:

1. A television transmitter for odd-line interlaced scanning at two fields per frame. comprising a scanning disk, said disk being provided with a peripheral rowof slots the number of -35 which is equal to the number of lines pe frame for producing the line synchronizing signals and a single slot for producing the field synchroniz ing signals, means for rotating said disk at 2N revolutions per frame where N is a whole num- 4 ber of the order of two or more, a separate light beam and photo-cell associated with the line synchronising slots and the field synchronizing slot for producing a first series of voltage variationsof 2N times the line frequency and a second series of voltage variations of H timesthe field frequency, respectively, means to reduce by 2N times the frequency of said first series of voltage variations. means to convert the reduced series into line synchronising impulses, means to reduce by N times the frequency of said second series of voltage variations to produce field synchronizing impulses. and means to combine the line and the field synchronising impulsu into a common composite series.

2. A television transmitter for odd-line interlaced scanning at two fields per frame, comprising a scanningdisk, said disk being piovided with a peripheral row ofslots the number of whichis equaito the number of lines per frame for, producing the line signals and a single slot for producing the field synchronizins signals, means for rotating saiddisk at four revolutions per frame,- a light beam and photocell as sociated with'the'peripheral slots for producing a first series of voltage variations of four times the line frequency, a second light beam and photo-cell associated with the field syn--- chronising slot for producing a second series of voltage variations of two times the field frequen vlmeansto reduce by one-fourth the frequency of said first series of voltage variations. means to convert the reduced series into line synchronizing impulses, means to reduce by one-half the frequency of said second series of voltage variations to produce field synchronizing impulsesrand means to combine the line and field syxnlchronizing impulses into a-single composite se es. 

